The present invention relates generally to long horizontal rolls and relates more particularly to adjustable sag type press rolls that are used in wet presses or calenders of paper machines, as well as machines for the working of other web materials, such as textile webs, plastic sheets or metal foils.
Adjustable sag type press rolls are described in U.S. Pat. No. 3,766,620, issued Oct. 23, 1973 to A.J. Roering for Controlled Deflection Roll Drive and in U.S. Pat. No. 4,000,979, issued June 4, 1977 to M. Biondetti for Roll For a Rolling Mill.
In accordance with U.S. Pat. No. 3,766,620, a roll shell is supported at each end on an extension ring and a self-aligning bearing disposed between the ring and a yoke. The latter extends through the roll shell and rests on a support pedestal. An outer gear rim, machined directly in the outer surface of the extension ring, and a drive pinion in mesh with the gear rim are disposed between the self-aligning bearing and the support pedestal. A gear housing for the pinion and gear rim is supported by a tubular collar piece located within the extension ring of the shell of the roll.
With the construction of U.S. Pat. No. 3,766,620, dimensioning for the seal between the gear housing and extension ring, and the rear bearing (bearing remote from the drive input) on the drive pinion is critical. Proper dimensioning is difficult because this seal and this bearing are positioned substantially in the same transverse plane normal to the roll axis, so that positioning considerations for these two elements often conflict with each other. That prior art construction also suffers from the fact that the self-aligning bearing between the extension and the yoke lies very close to the aforesaid transverse plane. Because of this the diameter of the sliding or working surface of the seal must be greater than the outside diameter of the self-aligning bearing and greater than the outside diameter of the gear rim on the extension ring. As a result, the seal wears relatively rapidly and the outside diameter of the rear bearing for the pinion must be relatively small. Theoretically, it is possible to provide a large rear bearing by enlarging the center-to-center distance between the pinion and gear on the extension ring, but by doing so the gear transmission ratio is reduced. This is undesirable since, as a rule, the highest possible speed of rotation of the pinion is desired.
In the construction of U.S. Pat. No. 4,000,979, the roll shell is mounted at each of its ends on a slotted link which is connected to the yoke in a nonrotatable but radially translatable manner. In this way, it is possible to shift the roll shell by a relatively large amount in a radial direction relative to the yoke, say in order to move the roll shell toward and away from a mating roll. The outer gear rim is developed as an extension ring of the roll shell, and the pinion lies approximately in the same transverse plane as the slotted link. In a similar prior art construction the gears are disposed between the slotted link and the outer support pedestal for the yoke. In both cases, the gear housing is mounted on the outside of the extension ring and extends over both sides of the outer gear rim.
One disadvantage of these slotted link constructions is that the gear housing must have a relatively large axial structural length in the region of the large diameter driven gear. Therefore, if the gearing is arranged between the slotted link and the support pedestal for the yoke, the space available in the axial direction is extremely small. Under certain circumstances it may even be necessary to shift the support pedestal outward and lengthen the yoke accordingly. If the gearing is arranged in the transverse plane of the slotted link, then the radial length of the gear housing necessarily becomes very large in the region of the driven outer gear.